Steering mechanism for bi-directional catheter

ABSTRACT

A bi-directional catheter with nearly double the throw in its catheter tip deflection defines a puller wire travel path having a U-turn a pulley which minimizes the offset angle between the puller wire and the longitudinal axis of the control handle while maximizing the travel distance of that puller wire for any given distance traveled by the pulley drawing the puller wire. In particular, the control handle of the catheter which includes a steering assembly having a lever arm carrying a pair of pulleys for drawing corresponding puller wires to deflect the tip section of the catheter. The pulleys are rotatably mounted on opposing portions of the lever arm such that one pulley is moved distally as the other pulley is moved proximally when the lever arm is rotated. Because each puller wire is trained on a respective pulley, rotation of the lever arm causes the pulley that is moved proximally to draw its puller wire to deflect the tip section in the direction of the off-axis lumen in which that puller wire extends.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.10/871,682 filed Jun. 14, 2004 and entitled STEERING MECHANISM FORBI-DIRECTIONAL CATHETER, the entire content of which is incorporatedherein by reference.

FIELD OF INVENTION

The present invention relates to improved bidirectional steerablecatheters, and more particularly to catheters having bidirectionalcontrol handles.

BACKGROUND OF INVENTION

Electrode catheters have been in common use in medical practice for manyyears. They are used to stimulate and map electrical activity in theheart and to ablate sites of aberrant electrical activity. In use, theelectrode catheter is inserted into a major vein or artery, e.g.,femoral artery, and then guided into the chamber of the heart which isof concern. Within the heart, the ability to control the exact positionand orientation of the catheter tip is critical and largely determineshow useful the catheter is.

Bidirectional catheters have been designed to be deflectable in onedirection by one puller wire and in the opposite direction within thesame plane by a second puller wire. In such a construction, the pullerwires extend into opposing off-axis lumens within the tip section of thecatheter. So that the tip section can bend in both directions in thesame plane, the puller wires and their associated lumens must be locatedalong a diameter of the tip section. For ablation catheters, electrodelead wires must also be provided within the distal end. Typically, anadditional lumen is used to contain the electrode lead wires. Forexample, U.S. Pat. No. 6,210,407, the disclosure of which isincorporated herein by reference, is directed to a bi-directionalcatheter comprising two puller wires and a control handle having atleast two moveable members longitudinally movable between first andsecond positions. The proximal end of each puller wire is connected toan associated movable member of the control handle. Proximal movement ofa movable member relative to the catheter body results in proximalmovement of the puller wire associated with that movable member relativeto the catheter body, and thus deflection of the tip section in thedirection of the lumen in which that puller wire extends

As another example, U.S. Pat. No. 6,171,277, the disclosure of which isincorporated herein by reference, is directed to a bidirectionalsteerable catheter having a control handle that houses agenerally-circular spur gear and a pair of spaced apart rack gears. Eachrack gear is longitudinally movable between first and second positions,whereby proximal movement of one rack gear results in rotationalmovement of the spur gear, and correspondingly distal movement of theother rack gear. Two puller wires extend from the control handle whosethe distal ends are fixedly attached to the tip section, and whoseproximal ends are each anchored to a separate associated rack gear inthe control handle. Proximal movement of a rack gear and its associatedpuller wire relative to the catheter body results in deflection of thetip section in the direction of the off axis lumen into which thatpuller wire extends.

Also known is U.S. Pat. No. 6,198,974, the disclosure of which isincorporated herein reference, is directed to a bi-directional electrodecatheter comprising a control handle. At their proximal ends, two pairsof puller wires are attached to movable pistons in the control handle.Each piston is controlled by an operator using a slidable button fixedlyattached to each piston. Movement of selected buttons results indeflection of the tip section into a generally planar “U”- or “S”-shapedcurve.

Further known is U.S. Pat. No. 5,891,088, the disclosure of which isincorporated, directed to a steering assembly with asymmetric left andright curve configurations. Proximal ends of left and right steeringwires are adjustably attached to a rotatable cam housed in a controlhandle. The rotatable cam has first and second cam surfaces which may beconfigured differently from each other to accomplish asymmetricsteering.

While the aforementioned catheters provide bi-directional steering, themechanical efficiencies of the steering or deflection mechanism can beimproved upon. Because the control handle has limited interior space inwhich to house the steering mechanism, a need exists for a compact yetmechanically-efficient design to accomplish bi-directional steering.Moreover, a greater degree of deflection in the catheter tip is alsodesirable, particularly if it can be accomplished without requiringgreater exertion on the part of the user. The steering assembly ofaforementioned U.S. Pat. No. 5,891,088 employs a configuration wherebythe puller wires extend to the cam surfaces of the rotatable cam at agreater than generally desirable angle from the longitudinal axis of thecatheter shaft, which decreases the efficiency of the steering lever andadds to friction losses in the operation of the steering assembly. Inaddition, the steering assembly therein generally limits the amount oflongitudinal movement of the puller wires for deflecting the cathetertip to only the circumference of the rotatable cam. An improved catheterwith bi-directional deflection is therefore desired.

SUMMARY OF THE INVENTION

The present invention provides a bi-directional catheter with nearlydouble the throw in its catheter tip deflection. In particular, thetravel path of each the puller wire includes a U-turn or doubling-backaround a pulley which minimizes the offset angle between the puller wireand the longitudinal axis of the control handle while maximizing thetravel distance of that puller wire for any given distance traveled bythe pulley drawing the puller wire.

In one embodiment, the catheter has an elongated catheter body, acatheter tip section with first and second diametrically-opposedoff-axis lumens, and a control handle which includes a steering assemblyhaving a lever arm carrying a pair of pulleys for drawing correspondingpuller wires to deflect the tip section of the catheter. The pulleys arerotatably mounted on opposing portions of the lever arm such that onepulley is moved distally as the other pulley is moved proximally whenthe lever arm is rotated. Because each puller wire is trained on arespective pulley, rotation of the lever arm causes the pulley that ismoved proximally to draw its puller wire to deflect the tip section inthe direction of the off-axis lumen in which that puller wire extends.

In a detailed embodiment of the invention, each puller wire is trainedabout its respective pulley for at least about 180 degrees. Moreover,each puller wire may extend from the distal end of the control handle toits respective pulley at a predetermined angle generally less than 10degrees from the longitudinal axis of the control handle. Furthermore,the range of rotation of the lever arm deflecting the catheter tip canbe predetermined through a predetermined profile or curvature in thehousing of the control handle.

In another embodiment of the invention, the catheter includes a pair ofconstant force springs that draw up slack in a puller wire when the tipis deflected. The catheter may also include a pair of adjustable stopsthat are configured to prevent proximal movement of each proximal end ofthe puller wires beyond a respective predetermined stop location in thecontrol handle. Coarse and fine adjustments in each stop location areaccomplished through adjustable positioning and configuration of thestops within the catheter housing.

In yet another embodiment, the catheter includes a deflection knob thatis rotationally coupled to the lever arm which enables the user tocontrol deflection of the tip section with, preferably, a thumb and anindex finger, when grasping the control handle. The catheter may alsoinclude a tension adjustment mechanism for adjusting the tightness ofthe deflection knob.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a side view of an embodiment of the catheter of the invention.

FIG. 2 is a side cross-sectional view of the junction of the catheterbody and tip section of an embodiment of a catheter according to theinvention.

FIG. 3 is a transverse cross-sectional view of the catheter body shownin FIG. 2 taken along line 3-3.

FIG. 4 is a side cross-sectional view of the distal end of the tipsection shown in FIG. 2.

FIG. 5 is a transverse cross-sectional view of the tip section alongline 5-5.

FIG. 6 is a transverse cross-sectional view of a catheter tip sectionaccording to the invention where the puller wires are anchored to theside walls of the tip section.

FIG. 7 is a longitudinal cross-sectional view of a preferred puller wireT-bar anchor.

FIG. 8 is a longitudinal cross-sectional view of the puller wire T-baranchor of FIG. 7 rotated 90.degree. to show the cross-piece on end.

FIG. 9 is a top exploded view of a control handle of the catheter ofFIG. 1.

FIG. 10 is a view of a control handle of the catheter of FIG. 9 takengenerally along Line V-V with parts broken away for clarity.

FIG. 10 a is a view of the control handle of FIG. 10 taken generallyalong Line W-W.

FIG. 11 shows components of the steering assembly without deflection inthe tip section of the catheter.

FIG. 12 shows components of the steering assembly for deflection of thetip section to the right.

FIG. 13 shows components of the steering assembly for deflection of thetip section to the left.

FIG. 14 is a side view of a free end of a spring fastened to a proximalend of a puller wire by a crimp fastener.

FIG. 15 is a side view of a free end of a spring fastened to a proximalend of a puller by a welded joint.

DETAILED DESCRIPTION OF THE INVENTION

In an embodiment of the invention, there is provided a steerablebidirectional electrode catheter. As shown in FIG. 1, the catheter 10comprises an elongated catheter body 12 having proximal and distal ends,a tip section 14 at the distal end of the catheter body 12, and acontrol handle 16 at the proximal end of the catheter body 12.

As shown in FIGS. 2 and 3, the catheter body 12 comprises an elongatedtubular construction having a single axial or central lumen 18. Thecatheter body 12 is flexible, i.e., bendable, but substantiallynon-compressible along its length. The catheter body 12 can be of anysuitable construction and made of any suitable material. A presentlypreferred construction comprises an outer wall 20 made of polyurethaneor PEBAX. The outer wall 20 preferably comprises an imbedded braidedmesh of stainless steel or the like to increase torsional stiffness ofthe catheter body 12 so that when the control handle 16 is rotated thetip section 14 will rotate in a corresponding manner.

The overall length and diameter of the catheter 10 may vary according tothe application. A presently preferred catheter 10 has an overall lengthof about 48 inches. The outer diameter of the catheter body 12 is notcritical, but is preferably no more than about 8 french. The innersurface of the outer wall 20 is preferably lined with a stiffening tube22, which can be made of any suitable material, preferably nylon orpolyimide. The stiffening tube 22, along with the braided outer wall 20,provides improved flexural and torsional stability while at the sametime minimizing the wall thickness of the catheter body 12, thusmaximizing the diameter of the central lumen 18. The outer diameter ofthe stiffening tube 22 is about the same as or slightly smaller than theinner diameter of the outer wall 20. A particularly preferred catheter10 has an outer diameter of about 0.092 inch and a lumen 18 diameter ofabout 0.052 inch.

As shown in FIGS. 4 and 5, the tip section 14 comprises a short sectionof flexible tubing 24 having a first off-axis lumen 26 and a secondoff-axis lumen 28. The flexible tubing 24 is made of a suitablenon-toxic material that is preferably more flexible than the catheterbody 20. A presently preferred material for the tubing 24 is braidedpolyurethane, i.e., polyurethane with an embedded mesh of braidedstainless steel or the like. The outer diameter of the tip section 14,like that of the catheter body 12, is preferably no greater than about 7french, more preferably about 6½ french or less.

The off-axis lumens 26, 28 extend through diametrically opposed halvesof the tip section 14. The off-axis lumens 26, 28 are asymmetrical andtherefore non-interchangeable. The first off-axis lumen 26 is smallerthan the second off-axis lumen 28. In an 8 french or 7 french diametercatheter, where the tip section is 6½ french, it is preferred that thefirst off-axis lumen 26 has a diameter ranging from about 0.018 inch toabout 0.025 inch, more preferably from about 0.018 inch to about 0.022inch. Preferably, the second off-axis lumen 28 has a diameter rangingfrom about 0.022 inch to about 0.030 inch, more preferably from about0.026 inch to about 0.028 inch.

By using two rather than three lumens along a single diameter, thepresent design retains the simplified construction of the unidirectionaldeflectable steerable catheter described in U.S. Pat. No. Re 34,502,which is incorporated herein by reference. However, it is understoodthat additional lumens may be provided in the tip section. As describedin U.S. Pat. No. 6,171,277, the disclosure of which is incorporatedherein by reference, the tip section 14 may contain four lumens, two ofwhich have a greater diameter of about 0.029 inch and two of which havea lesser diameter of about 0.018 inch. Lead wires for the electrodes,thermocouple wires and/or electromagnetic sensor cable may extendthrough different lumen(s) from those through which each of puller wiresextends. As such, the present invention may employ two or more lumens inthe tip section 14.

A preferred means for attaching the catheter body 12 to the tip section14 is illustrated in FIG. 2. The proximal end of the tip section 14comprises an outer circumferential notch 34 that receives the innersurface of the outer wall 20 of the catheter body 12. The tip section 14and catheter body 12 are attached by glue or the like. Before the tipsection 14 and catheter body 12 are attached, however, the stiffeningtube 22 is inserted into the catheter body 12. The distal end of thestiffening tube 22 is fixedly attached near the distal end of thecatheter body 12 by forming a glue joint with polyurethane glue or thelike. Preferably a small distance, e.g., about 3 mm, is provided betweenthe distal end of the catheter body 12 and the distal end of thestiffening tube 22 to permit room for the catheter body 12 to receivethe notch 34 of the tip section 14. A force is applied to the proximalend of the stiffening tube 22, and, while the stiffening tube 22 isunder compression, a first glue joint (not shown) is made between thestiffening tube 22 and the outer wall 20 by a fast drying glue, e.g.Super Glue®. Thereafter a second glue joint is formed between theproximal ends of the stiffening tube 22 and outer wall 20 using a slowerdrying but stronger glue, e.g., polyurethane.

A spacer 36 lies within the catheter body 12 between the distal end ofthe stiffening tube 22 and the proximal end of the tip section 14. Thespacer 36 is preferably made of a material that is stiffer than thematerial of the tip section 14, e.g., polyurethane, but not as stiff asthe material of the stiffening tube 22, e.g. polyimide. A spacer made ofTeflon® is presently preferred. A preferred spacer 36 has a length offrom about 0.25 inch to about 0.75 inch, more preferably about 0.50inch. Preferably the spacer 36 has an outer and inner diameter about thesame as the outer and inner diameters of the stiffening tube 22. Thespacer 36 provides a transition in flexibility at the junction of thecatheter body 12 and the tip section 14 to bend smoothly without foldingor kinking.

In the depicted embodiment, the distal end of the tip section 14 carriesa tip electrode 38 (see FIGS. 1 and 4). Mounted along the length of thetip section 14 is a ring electrode 40 (see FIG. 4). The length of thering electrode 40 is not critical, but is preferably about 1 mm to about3 mm.

Additional ring electrodes can be provided if desired. If multiple ringelectrodes are used, they are spaced apart in any fashion as desired solong as their edges do not touch.

As shown in FIGS. 2-5, the tip electrode 38 and ring electrode 40 areeach connected to a separate lead wire 30. Each lead wire 30 extendsthrough the second off-axis lumen 28 in the tip section 14 (FIG. 5),through the central lumen 18 in the catheter body 12 (FIG. 3) andthrough the control handle 16. The proximal end of each lead wire 30extends out the proximal end of the control handle 16 and is connectedto an appropriate connector, which can be plugged into or otherwiseconnected to a suitable monitor, source of energy, etc.

The lead wires 30 are connected to the tip electrode 38 and ringelectrode 40 by any conventional technique. Connection of a lead wire 30to the tip electrode 38 is preferably accomplished by solder or thelike. Connection of a lead wire 30 to the ring electrode 40 ispreferably accomplished by first making a small hole through the tubing24. Such a hole can be created, for example, by inserting a needlethrough the tubing 24 and heating the needle sufficiently to form apermanent hole. The lead wire 30 is then drawn through the hole by usinga microhook or the like. The end of the lead wire 30 is then stripped ofany coating and welded to the underside of the ring electrode 40, whichis then slid into position over the hole and fixed in place withpolyurethane glue or the like.

As also shown in FIGS. 2-5, two puller wires 32 extend through thecatheter 10. Each puller wire 32 extends from the control handle 16,through the central lumen 18 in the catheter body 12 (FIG. 3) and intoone of the off-axis lumens 26 and 28 of the tip section 14 (FIG. 5). Asdescribed in more detail below, the proximal end of each puller wire 32is anchored within the control handle 16 and the distal end of eachpuller wire 32 is anchored within the tip section

Each puller wire 32 is made of any suitable metal, such as stainlesssteel or Nitinol. Preferably each puller wire 32 has a coating, such asa coating of Teflon® or the like. Each puller wire 32 has a diameterpreferably ranging from about 0.006 inch to about 0.0010 inch.Preferably both of the puller wires 32 have the same diameter.

Each puller wire 32 is anchored near the distal end of the tip section14. In the embodiment depicted in FIG. 4, the puller wires 32 are bothanchored to the tip electrode 38 by a welding or the like.

Alternatively, the puller wire 32 in the first off-axis lumen 26 can beanchored to the side wall of the tip section 14. As shown in FIGS. 7 to9, the puller wire 32 is preferably attached by means of an anchor 44fixedly attached to the distal end of the puller wire 32. The anchor 44is formed by a metal tube 45, e.g., a short segment of hypodermic stock,that is fixedly attached, e.g. by crimping, to the distal end of thepuller wire 32. The tube has a section that extends a short distancebeyond the distal end of the puller wire 32. A cross-piece 47 made of asmall section of stainless steel ribbon or the like is soldered orwelded in a transverse arrangement to the distal end of the metal tubewhich is flattened during the operation. This creates a T-bar anchor 44.A notch is created in the side of the tip section 14 resulting in anopening in the off-axis lumen 26 carrying the puller wire 32. The crosspiece 47 lies transversely within the notch. Because the length of theribbon forming the cross-piece 47 is longer than the diameter of theopening into the off-axis lumen 26, the anchor 44 cannot be pulledcompletely into the off-axis lumen 26. The notch is then sealed withpolyurethane glue or the like to give a smooth outer surface. The glueflows into the off-axis lumen 26 to fully secure the anchor. A tunnel,in the form of polyimide tubing or the like, can be provided to permitpassage of the lead wire 30 through the glue so that this same pullerwire anchor construction can be used in the second off-axis lumen 28.Other means for anchoring the puller wires 32 in the tip section 14would be recognized by those skilled in the art and are included withinthe scope of the invention.

Referring back to FIGS. 1 and 2, the catheter 10 further comprises twocompression coils 46, each in surrounding relation to a correspondingpuller wire 32. Each compression coil 46 is made of any suitable metal,such as stainless steel. Each compression coil 46 is tightly wound onitself to provide flexibility, i.e., bending, but to resist compression.The inner diameter of each compression coil 46 is slightly larger thanthe diameter of its associated puller wire 32. For example, when apuller wire 32 has a diameter of about 0.007 inch, the correspondingcompression coil 46 preferably has an inner diameter of about 0.008inch. The coating on the puller wires 32 allows them to slide freelywithin the compression coil 46. The outer surface of each compressioncoil 46 is covered along most of its length by a flexible,non-conductive sheath 48 to prevent contact between the compression coil46 and the lead wires 30 within the central lumen 18. The non-conductivesheath 48 made of thin-walled polyimide tubing is presently preferred.

As shown in FIG. 2, at the distal end of the catheter body, the twocompression coils 46 are positioned in diametric opposition within thestiffening tube 22 and spacer 36 so that they can be aligned with thetwo off-axis lumens 26,28 in the tip section 14. The compression coils46 and stiffening tube 22 are sized so that the compression coils 46 fitclosely and slidably within the stiffening tube 22. With this design,the lead wires 30 distribute themselves around the two compression coils46 without misaligning the coils.

The compression coils 46 are secured within the catheter body 12 withpolyurethane glue or the like. Each compression coil 46 is anchored atits proximal end to the proximal end of the stiffening tube 22 in thecatheter body 12 by a glue joint (not shown). When a stiffening tube 22is not used, each compression coil is anchored directly to the outerwall 20 of the catheter body 12.

Still referring to FIG. 2, the distal end of each compression coil 46 isanchored to the distal end of the stiffening tube 22 in the catheterbody 12 by a glue joint 52, or directly to the distal end of the outerwall 20 of the catheter body 12 when no stiffening tube 22 is used.Alternatively, the distal ends of the compression coils 46 may extendinto the off-axis lumens 26, 28 of the tip section 14 and are anchoredat their distal ends to the proximal end of the tip section 14 by a gluejoint. In the depicted embodiment, where the compression coils 46 areeach surrounded by the sheath 48, care should be taken to insure thatthe sheath is reliably glued to the compression coil. The lead wires 30can also be anchored in the glue joint. However, if desired, tunnels inthe form of plastic tubing or the like can be provided around the leadwires at the glue joint to permit the lead wires to be slidable withinthe glue joint.

Both glue joints preferably comprise polyurethane glue or the like. Theglue may be applied by means of a syringe or the like through a holemade between the outer surface of the catheter body 20 and the centrallumen 18. Such a hole may be formed, for example, by a needle or thelike that punctures the outer wall 18 and the stiffening tube 22 that isheated sufficiently to form a permanent hole. The glue is thenintroduced through the hole to the outer surface of the compression coil46 and wicks around the outer circumference to form a glue joint aboutthe entire circumference of each sheath 48 surrounding each compressioncoil 46. Care must be taken to insure that glue does not wick over theend of the coil so that the puller wire cannot slide within the coil.

As best shown in FIGS. 2 and 5, within the off-axis lumens 26, 28, eachpuller wire 32 is surrounded by a plastic sheath 42, preferably made ofTeflon®. The plastic sheaths 42 prevent the puller wires 32 from cuttinginto the wall of the tip section 14 when the tip section is deflected.Each sheath 42 ends near the distal end of each puller wire 32.Alternatively, each puller wire 32 can be surrounded by a compressioncoil where the turns are expanded longitudinally, relative to thecompression coils extending through the catheter body, such that thesurrounding compression coil is both bendable and compressible.

Longitudinal movement of the puller wires 32 relative to the catheterbody 12, which results in deflection of the tip section 14, isaccomplished by manipulation of the control handle 16. A suitablebidirectional control handle for use in the present invention isillustrated in FIGS. 9-15.

As shown in FIG. 9, the control handle 16 comprises a generallyelongated handle housing 60, which can be made of any suitable rigidmaterial. The housing 60 can be of a unitary construction or of twoopposing halves 64, 66 that are joined by glue, sonic welding or othersuitable means along a longitudinal peripheral seam 67. The controlhandle 16 comprises a steering assembly 68 that controls deflection ofthe tip section in response to manipulations by the user. In theillustrated embodiment, the steering assembly comprises a lever arm 70carrying a pair of coordinated pulleys 72 that act on the puller wires32 to deflect the tip section. The lever arm 70 of the steering assembly68 is seated for rotation between a top washer 80 and a bottom washer82. A friction nut 84 and a pin 86 couple an external deflection knob 88to the lever arm. The deflection knob seats against an O-ring 90.Movement of the deflection knob 88 by the user rotates the lever arm 70about a screw 98 within the housing 60, as explained below in furtherdetail. Contact between deflection knob 88 and the side of the housing60 physically limits the range of left and right rotation of the leverarm about a throw axis 75.

The steering assembly 68 also includes an external tension adjustmentknob 94 that an adhesive couples to the head of the screw 98. Thetension adjustment knob 94 seats against another O-ring 96. Movement ofthe knob 94 rotates the screw 98. Clockwise rotation of the knob 94tightens the screw 98 to increase the seating force between the leverarm and the bottom washer 82. When moved fully clockwise to contactagainst the housing, the knob 94 imposes a seating force that preventsrotation of the lever arm 70 by the deflection knob 88. Counterclockwisemovement of the tension adjustment knob 94 loosens the screw 98 todecrease the seating force and free the lever arm 70 for rotation.

As shown in FIG. 10, the lever arm 70 has a rotation angle about a throwaxis 75, which is generally perpendicular to a longitudinal axis 77 ofthe control handle 16. A neutral position along axis 102 is defined forthe lever arm when its longitudinal axis 104 is generally perpendicularto the longitudinal axis 77 of the control handle 16. The lever arm isrotatable from its neutral position in the clockwise direction by angle+α and in the counterclockwise direction by angle −α. Because the leverarm is rotationally coupled to the deflection knob 88, the range of theangle α is also limited by the contact of the deflection knob 88 withthe housing 60. In the disclosed embodiment, the angle α ranges betweenabout 0 and 70 degrees, preferably between about 30 and 60 degrees andmore preferably between about 40 to 50 degrees. Accordingly, thedisclosed embodiment provides a total range of rotation (from −β to +α)of between about 0 and 140 degrees, preferably between about 60 and 120degrees and more preferably between about 80 to 100 degrees.

The pulleys 72 are located at opposing ends of the lever arm 70, at aradial distance R from the throw axis 75. As shown in FIGS. 11-13, withrotation of the lever arm 70, one pulley 72 is translated distally asthe other pulley 72 is translated proximally. Moreover, each pulley canrotate counterclockwise or clockwise about its own axis of rotation.

In accordance with the present invention, the steering assembly 68 isadvantageously configured to provide a relatively shorter angular throwwhile increasing, if not at least generally doubling, the throw capacityof the catheter. In particular, the steering assembly has a minimizedmoment of inertia about the throw axis 75, while generally doubling thetravel distance of a puller wire in relation to the travel distance ofthe respective pulley drawing that puller wire, despite the relativelysmall interior of the housing. Moreover, the steering assembly providesa minimal angle between the longitudinal axis 77 of the control handle16 and a segment of the puller wire drawn to accomplish deflection, formore efficient use of the force applied by the user in operating thecontrol handle. To facilitate these movements for deflecting the tipsection, the steering assembly 68 also includes a pair of constant forcesprings 74 that are attached to the proximal ends of the puller wires,and a pair of adjustable stops 76 which prevent the proximal ends of thepuller wires from moving proximally past a selected position relative tothe longitudinal axis of the control handle.

Referring back to FIG. 10, the housing 60 is configured at its distalend with a port 90 through which proximal end segments of the pullerwires 32 enter the control handle 16. In the housing half 66, a divider92 is configured in the inner surface and distal of the port to extendlinearly between the port and the lever arm 70. At a distal end 94 ofthe divider, the puller wires (now designated as 32 a, 32 b) divergetoward a respective pulley 72 in the lever arm. For ease of discussion,the housing half 66 may be described as divisible along the divider 92into top and bottom housing quarters 96 a, 96 b, which are more or lessmirror counterparts of each other in terms of physical layout andoperation. Accordingly, the following description uses similar referencenumerals for similar structures except the numerals are followed by theletter a or the letter b.

The puller wire 32 a continues from the port 90 proximally in aminimally diagonal and generally linear direction toward the pulley 72 ain the lever arm 70. At the pulley 72 a, the puller wire 32 a is trainedcounterclockwise about the pulley before it extends distally toward thespring 74 a where its proximal end (so designated despite its beingphysically distal of a preceding segment) is attached to a free end 109a of the spring 74 a by a fastener 111 a, such as a welded joint 113(FIG. 14) or a crimp fastener 114 (FIG. 15).

Correspondingly, the puller wire 32 b continues from the port proximallyin a minimally diagonal and generally linear direction toward the pulley76 b in the lever arm 70. At the pulley, the puller wire 32 b is trainedclockwise about the pulley before it extends distally toward the spring74 b where its proximal end, (so designated despite its being physicallydistal of a preceding segment) is attached to a free end 109 b of thespring 74 b by a fastener 111 b, such as the welded joint 113 or thecrimp fastener 114.

In the embodiment of FIG. 10, each puller wire is trained about itspulley for a predetermined degree ranging between about 185 to 215,preferably 190-210, or more preferably about 195-205. Moreover, in FIG.10, the springs 76 a, 76 b are illustrated as flat coil springs. Ingeneral, each spring member exerts a force in the distal directionranging between about 0.25 lbs. and 1.0 lbs, preferably ranging betweenabout 0.4 lbs and 0.8 lbs, and preferably of about 0.6 lbs.

In view of the foregoing, the travel path within the housing of eachpuller wire is as follows: a first generally linear path traversed bypuller wire segments 120 a, 120 b between the port 90 and the respectivepulley 72 a, 72 b, a non-linear (including, e.g., a U-turn or doublingback) path traversed by puller wire segments 122 a, 122 b generallyaround the respective pulley 72 a, 72 b, and a second generally linearpath traversed by puller wire segments 124 a, 124 b between therespective pulley 72 a, 72 b and the respective springs 74 a, 74 b. Inthat regard, the stops 76 a, 76 b guide the direction of travel of thesegments 120 a, 120 b and 124 a, 124 b . As best shown in FIG. 10 a,each stop has a first channel 130 in which one of the segments 120 a,120 b extends and a second channel 132 in which one of the segments 124a, 124 b extends. While the first and second channels are sized to allowthe wire segments to move distally or proximally, distal ends 135 a, 135b of the second channels are configured to prevent proximal end 138 a,138 b of the wires and/or the free ends 109 a, 109 b of the springs 74a, 74 b from moving proximally past the distal ends 135 a, 135 b. Thirdchannels 133 a, 133 b are provided so that other components of thecatheter body (e.g., lead wires, irrigation tubes, etc.) can passthrough the control handle without interfering with the steeringassembly 68 and movements of the puller wire.

Given the foregoing, it can be seen from FIGS. 11-13 that rotation ofthe lever member 70 causes deflection in the catheter tip section 14.That is, when the lever member is rotated in the clockwise rotation(namely, in the +α direction) (FIG. 13 b), the pulley 72 a is translatedproximally. Because the puller wire 32 a trained on the pulley 72 a isstopped at its proximal end by the stop 76 a, the proximal translationof the pulley 72 a causes it to rotate counterclockwise thereby drawingproximally the wire segment 120 a, which results in deflection of thetip section 14 to the right.

Facilitating this deflection is the release of the segment 124 b as thepulley 72 b is coincidentally translated distally by the lever arm 70.The resulting slack in the segment 124 b is taken up by the spring 74 b(a tubular coil spring in the illustrated embodiment) as the pulley 72 brotates clockwise.

Correspondingly, when the lever arm is rotated in the counterclockwiserotation (namely, in the −α direction) (FIG. 13 c), the pulley 72 b istranslated proximally. Because the puller wire 32 b trained on thepulley 72 b is stopped at its proximal end by the stop 76 b, theproximal translation of the pulley 72 b causes it to rotate clockwisethereby drawing proximally the wire segment 120 b, which results indeflection of the tip section 14 to the left. Facilitating thisdeflection is the release of the segment 124 a as the pulley 72 a iscoincidentally translated distally by the lever arm 70. The resultingslack in the segment 124 a is taken up by the spring 74 a (a tubularcoil spring in the illustrated embodiment) as the pulley 72 a rotatescounterclockwise.

Although each of the actuating pulley has translated proximally only adistance x (FIGS. 12 and 13) along the longitudinal axis 77 as a resultof the rotation of the lever arm 70, the length of the puller wire drawnby that pulley proximally from the port in deflecting the tip section isabout 2x. Consequently, the present invention provides a catheter withnearly double the throw in tip deflection, despite the small interiorspace of the control handle.

Moreover, as also shown in FIGS. 11-13, an angle of alignment of thesegments 120 a, 120 b deviates only minimally from the longitudinal axis77 which provides greater operating efficiency in the force required todeflection the tip section 14. In the disclosed embodiment, a deviationangle θ may range between about 5 to 12 degrees, preferably between 6and 10 degrees and more preferably between 7 and 8 degrees, when thelever arm is in the neutral position (namely, when α is at or near 0)(FIG. 11). Because the pulleys 72 each travel a circular path whentranslated by the lever arm 70, the angle θ can be further decreased byup to about 2-4 degrees (that is, down to about θ=3 degrees) during thistranslation (FIGS. 12, 13). In any case, given such a minimal range ofthe angle θ, most of the force that is applied to draw a puller wireproximally along the longitudinal axis 77 for deflecting the tip sectionin the direction of the off axis lumen in which that puller wire extendsis advantageously met by the proximal translation of the pulley drawingthat puller wire along the angle θ.

In accordance with the present invention, an initial neutral position(with little or no detectable deflection) (FIG. 11) in the tip section14 can be readily calibrated by selective placement of the stops 76 a,76 b distally or proximally along the divider 92. With the lever arm 70resting in the neutral position, the operating position of each pullerwire 32 is adjusted so that it is sufficiently taut in drawing the ends109 of the springs 74 against the stops 76 without causing anydetectable deflection in the tip section 14. In that regard, it isunderstood that the puller wires can also be adjusted to provide thecatheter with a predetermined amount of free play so that the catheterbody 12 and/or elements surrounding the puller wires (e.g., outer wall20 and/or stiffening tube 22) can shrink or stretch, such as duringsterilization of the catheter, without adversely deforming the pullerwires. These adjustments of the stop position of each puller wire canalso be made to compensate for certain characteristics in the catheter,including puller wires with unequal actual lengths and/or counterpartcomponents in the steering assembly or the control handle that are notexact duplicates of each other in terms of size or operatingcharacteristics.

In accordance with the present invention, each stop 76 a, 76 b isconfigured for coarse and fine adjustments of a stop location for eachpuller wire past which its proximal end (or its proximal end portion)cannot pass proximally. As described above in relation to FIGS. 11-13,the stop location of each stop 76 a, 76 b determines how much distancethe corresponding pulley needs to be moved (or the corresponding pullerwire needs to travel) proximally before the tip section 14 begins todeflect in that direction.

In enabling coarse (or incremental) adjustment in the stop position ofeach puller wire, each stop 76 a, 76 b is configured to adjustablyengage with the divider 92 at a selected position along the longitudinalaxis 77. In particular, an inner surface of each stop has a plurality ofprotrusions 136 that can engage with any of a series of recessions 138formed on either side of the divider 92. As such, the position of eachstop can be adjusted proximally or distally within the control handlealong the axis 77, thereby adjusting proximally or distally the stoplocation.

In enabling fine adjustment, a set screw 140 a, 140 b is provided at thedistal end 135 a, 135 b of each second channel 132 a, 132 b, where adistal end of each set screw can be moved proximally or distally byadvancing or withdrawing the screws in the channels. A tunnel in thescrew allows the puller wires to pass through and move distally orproximally through the screws, but the tunnel is sized to prevent thefasteners 111 a, 111 b, and/or the free end 109 a, 109 b of the springs74 a, 74 b from moving proximally past the distal ends of the setscrews. Accordingly, each set screw can be adjusted proximally ordistally within the control handle relative to the axis 77, therebyenabling fine adjustment proximally or distally of the stop location foreach puller wire.

Stop adjustments should be performed to attain a neutral position withlittle or no detectable deflection in the catheter tip section 14 beforethe housing halves 64, 66 are joined to each other. Significantly, thecontrol handle 16 is configured such that it need not be fully assembledfor the steering assembly 68 and deflection of the tip section 14 to beeffectively tested and evaluated. In particular, the steering assembly68 can be tested and evaluated when assembled within the housing half 66and operated on by the deflection knob 88 mounted on the lever arm 70without the housing half 64.

In other embodiments, one or more additional off axis lumens may beprovided through which additional components, e.g., infusion tube, opticfiber, etc., may extend. Depending on the intended use of the catheter10, it can further comprise additional features such as temperaturesensing means, an optic fiber, an infusion tube, and/or anelectromagnetic sensor. Additionally, smaller components, such as atemperature sensing means, could also extend through the second lumen inthe tip section along with the puller wire and lead wire(s).

In the embodiments described above, the central lumen 18 of the catheterbody 12 is used for passage of the electrode lead wires 30 as well asthe two puller wires 32, compression coils 46 and, if present,thermocouple wires, electromagnetic sensor cable, optic fiber orinfusion tube. It is understood that the catheter body 12 couldalternatively comprise a plurality of lumens. However, the singlecentral lumen 18 is preferred because it has been found that a singlelumen body permits better control when rotating the catheter 10. Thesingle central lumen 18 permits the puller wires 32, compression coils46 and lead wires 30 to float freely within the catheter body 12. Ifsuch wires are restricted within multiple lumens, they tend to build upenergy when the control handle 16 is rotated, resulting in the catheterbody 12 having a tendency to rotate back if, for example, the handle 16is released, or if bent around a curve, to flip over, either of whichare undesirable performance characteristics.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention.

Accordingly, the foregoing description should not be read as pertainingonly to the precise structures described and illustrated in theaccompanying drawings, but rather should be read consistent with and assupport to the following claims which are to have their fullest and fairscope.

1. A bi-directional catheter comprising: an elongated catheter bodyhaving proximal and distal ends; a catheter tip section at the distalend of the catheter body and having proximal and distal ends and firstand second diametrically-opposed off-axis lumens; a tip electrode at thedistal end of the catheter tip section; a control handle at the proximalend of the catheter body, the control handle having a longitudinal axisand comprising at least a steering assembly having a lever arm rotatableabout an axis substantially perpendicular to the longitudinal axis, thesteering assembly including at least two pulleys rotatably mounted onopposing portions of the lever arm; first and second puller wires, eachpuller wire having proximal and distal ends and extending from thecontrol handle through the catheter body, wherein the first puller wireextends into the first lumen in the tip section and the second pullerwire extends into the second lumen in the tip section, and wherein thedistal end of each puller wire is anchored to the tip section; and afirst stop member that defines a first stop position for the firstpuller wire and a second stop member that defines a second stop positionfor the second puller wire; wherein each puller wire is trained on arespective pulley and rotation of the lever arm results in proximalmovement of one of said pulleys relative to the control handle therebydrawing proximally at least a segment of its respective puller wire fordeflecting the tip section in the direction of the off-axis lumen inwhich that puller wire extends; and wherein each stop position isadjustable proximally and distally within the control handle.
 2. Abi-directional catheter of claim 1, further comprising at least one ringelectrode
 3. A bi-directional catheter of claim 1, wherein each of thepuller wires is trained about its respective pulley for at least about180 degrees.
 4. A bi-directional catheter of claim 1, wherein eachpuller wire extends from the distal end of the control handle to itsrespective pulley at an angle of no greater than about 10 degrees fromthe longitudinal axis of the control handle.
 5. A bi-directionalcatheter of claim 1, wherein each puller wire extends from the distalend of the control handle to its respective pulley at an angle rangingbetween about 7 and 10 degrees from the longitudinal axis of the controlhandle.
 6. A bi-directional catheter of claim 1, wherein the controlhandle further comprises a deflection knob, wherein the deflection knoband the lever arm are rotationally coupled to each other.
 7. Abidirectional catheter of claim 1, further comprising first and secondconstant force springs, each having a free end that is attached to aproximal end of a different puller wire.
 8. A bi-directional catheter ofclaim 7, wherein the constant force springs are positioned distal of thepulleys.
 9. A bi-directional catheter of claim 7, wherein the first andsecond stop members are positioned proximally of their respectivesprings.
 10. A bi-directional catheter of claim 1, further comprising adivider extending along the longitudinal axis of the control handle,said divider directing the puller wires at a predetermined angle towardtheir respective pulleys.
 11. A bi-directional catheter of claim 6,further comprising an adjustment knob configured to adjust tension ofthe deflection knob.
 12. A bi-directional catheter of claim 10, whereineach stop is adjustably engaged with the divider.
 13. A bi-directionalcatheter of claim 1, wherein each stop comprises means for finelyadjusting the stop position.
 14. A bi-direction catheter of claim 13,wherein the means for finely adjusting comprises a set screw.
 15. Abi-directional catheter of claim 1, wherein each stop member isconfigured to guide at least a segment of its respective puller wire.16. A bi-directional catheter comprising: an elongated catheter bodyhaving proximal and distal ends; a catheter tip section at the distalend of the catheter body and having proximal and distal ends and firstand second diametrically-opposed off-axis lumens; a tip electrode at thedistal end of the catheter tip section; a control handle at the proximalend of the catheter body, the control handle having a longitudinal axisand comprising at least a steering assembly having a lever arm rotatableabout an axis substantially perpendicular to the longitudinal axis, thelever arm having two pulleys rotatably mounted thereon; first and secondpuller wires, each puller wire having proximal and distal ends andextending from the control handle through the catheter body; means foradjustably setting a stop position for each puller wire; and wherein thefirst puller wire extends into the first lumen in the tip section andthe second puller wire extends into the second lumen in the tip section,and wherein the distal end of each puller wire is anchored to the tipsection, and wherein a travel path of each puller wire within thecontrol handle includes a turn away from the longitudinal axis of atleast 180 degrees about a respective pulley; and wherein rotation of thelever arm results in movement of one of said pulleys relative to thecontrol handle thereby drawing at least a segment of its respectivepuller wire for deflecting the tip section in the direction of theoff-axis lumen in which that puller wire extends.
 17. A bi-directionalcatheter of claim 16, further comprising at least one ring electrode.18. A bi-directional catheter of claim 16, wherein the proximal end ofeach puller wire is connected to a constant force spring.
 19. Abi-directional catheter of claim 16, wherein a travel distance of asegment of a puller wire drawn by a pulley for deflection is about twicethe travel distance of that pulley.
 20. A bi-directional catheter ofclaim 16, wherein a segment of a puller wire drawn by a pulley fordeflection extends at an angle of less than about 7 degrees from thelongitudinal axis.
 21. A bi-directional catheter of claim 16, whereinthe means for stopping comprises stop members, each of which releasablyengages with an elongated member extending along the longitudinal axisof the control handle.
 22. A bi-directional catheter of claim 21,wherein the general proximal end of each puller wire is prevented frommoving proximally past its stop position.
 23. A bi-directional cathetercomprising: an elongated catheter body having proximal and distal ends;a catheter tip section at the distal end of the catheter body and havingproximal and distal ends; a tip electrode at the distal end of thecatheter tip section; a control handle at the proximal end of thecatheter body, the control handle having a longitudinal axis andcomprising at least a steering assembly having a lever arm rotatableabout a throw axis, the steering assembly including at least two pulleysrotatably mounted on opposing portions of the lever arm; first andsecond puller wires, each puller wire having proximal and distal endsand extending from the control handle through the catheter body; and afirst stop member that defines a first stop position for the firstpuller wire and a second stop member that defines a second stop positionfor the second puller wire; wherein each puller wire is trained on arespective pulley and rotation of the lever arm results in proximalmovement of one pulley and distal movement of the other pulley, the onepulley moved proximally drawing proximally at least a segment of itsrespective puller wire for deflecting the tip section.
 24. Abidirectional catheter of claim 23, further comprising at least one ringelectrode.